Anatoxin-a is a naturally occurring, potent neurotoxin produced by some species of blue-green algae. Release of anatoxin-a into water bodies on cell lysis is of concern to farmers, whose livestock may be affected by drinking contaminated water; to recreational users of reservoirs where a blue-green algal scum is present; and to water companies, who need to be certain that levels of anatoxin-a in the water distribution system present no threat to public health. The present work describes the extraction and analysis of anatoxin-a from water samples. Extraction was performed using a polymeric resin solid-phase extraction cartridge, and analysis of the resulting extract was by reverse phase HPLC with UV detection. Data are presented describing the performance characteristics of the method, including limit of detection, precision, bias and recovery.